By Dan Weisz
Leucism (pronounced Loo-sism) is a condition where there is a loss of pigmentation causing a bird to have white feathers. It is overall pretty rare. Leucistic (pronounced Loo-siss-tick) birds show a variable amount of white or pale in the plumage. A friend told me about a leucistic Red-tailed Hawk in Pinal County so I went looking for it last week and I found it!!
The upper sides of the wing feathers were very dramatic with white feathers interspersed among the very dark feathers.
Leucism is caused by a genetic mutation that prevents the production of melanin in the bird’s cells. The condition is variable among birds and can result in bold white patches where there should be none, or paler overall plumage that looks faint or bleached, or overall white plumage with little or no color visible.
Red-tailed Hawks are territorial and during winter may congregate more closely than they would during breeding season. At one point a dark morph Red-tailed Hawk became very upset that the leucistic hawk was perched near it. The darker bird buzzed the leucistic hawk repeatedly trying to harass and chase it off. The leucistic bird kept its ground and eventually the darker bird flew off. While I was used to seeing Red-tailed Hawks often perching on the top of telephone poles, in this farmland and open country all of the Red-tails were perched near the top of mesquite tree during my morning visit, leaving the poles alone.
As often happens in birds, a feather can have different amount of pigmentation on opposite sides. In this hawk’s wing feathers, they were much darker on the upper side than they were on the lower side.
Here is a better look at the contrasting look of the upper top and underside of the wing feathers. This bird would fly very low to the ground as it moved around the area.
As it perched, you could see the typically red tail this bird is named for.
Albinism is different from leucism. An albino bird would have no pigment at all in any of its feathers or its skin. Albino birds would show pale pink or reddish eyes, legs and bill. Leucistic birds usually have normally colored eyes, legs, feet and bills.
And then it took off again!
And it turned and disappeared to the north. I took that as a sign for me to head home too.
Leucism is sometimes pronounced “luke-ism” so you are welcome to use whichever pronunciation that feels better for you. For a number of years there was a well-known Phainopepla in Sabino Canyon. Phainopeplas are known to be a glossy black color. This one had a white patch on its head. And so, the volunteers at Sabino Canyon referred to the bird as “Luke”. It would return to the same area of Sabino Canyon every winter.
For a Birdnote story on leucism, go to https://www.birdnote.org/listen/shows/why-my-robin-half-white